Electric heating element



2 Stunts-heey 1 W. W. WEIR ELECTRIC HEATING ELEMENT Filed QSC. 20, 1

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Sept. 8, 1925.

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Sept. 8, 1925. 1,553,209

W. W. WEIR ELECTRIC HEATING ELEMENT Filed Dec; 20, 1923 2 Shoots-Sheet 2 Fll.

Patented Sept. 8, 1925.

UNITED STATES PATENT OFFICE. y.

WILLIAM W. WEIR, 0F ALAMEDA, CALIFORNIA.

ELECTRIC HEATING ELEMENT.

Application mea December 2o, 192s. serial no. 681,797.

To a-ZZ whom t may concern:

Be it known that I, WILLIAM: W. WEIR, a citizen of the United States, and a resident of the city of Alameda, in the county of Alameda and State of California, have invented a new and useful Electric Heating Element, of which the following is a specication. A

, This invention relates to an electrical heating unit, and more. particularly to an element especially adapted to be used in ovens of electric ranges.

In these elements, the resistance wire is usually operated at such a temperature that deterioration, with consequent necessity to replace it, results. The replacement of this wire in previous types of elements is laborious and time consuming, and it is one of the objects of my invention to make it possible to replace or assemble such units with facility.

It is another 'object of my invention to simplify and improve; in general the con-- struction of such elements, whereby they may be inexpensively produced.

My invention possesses other advantageous features, some of which with the foregoing, will be set forth at length in`the following description, where I shall outline in full that form of the invention which I- have selected for illustration in the drawings accompanying and forming part of the present specification. Although I have shownin the drawings butone form of my invention, it is to be understood that I dov not desire to be limited thereto, since the invention as expressed in theclaims may be embodied in other forms also. Referring tothe drawings:

Figure 1 is a plan view of an oven ele` ment constructed inl accordance with my invention Fig. 2 is aside elevation of the ele-ment shown in Fig. 1;

Fig. 3 is a sectional view along plane 3 3 ofFig. l, butwith the element considerably shortened, so as t0 permit the use ofa large scale;

Fin'. 4 isa side elevation of one of the hooks used to hold the resistance coil in place;

Fig. 5 is a sectional view taken along plane 5-5 of Fig. 4.; and

Fig. 6 is a plan view of the hook shown in Fig. 4. f

I have shown in the present instance, two helically wound resistance coils 11 and 12, which serve as the conductors heated to the proper degree by the passage of an electri'c current. The wire used may be of michrome or other material having suitable electrical properties. The provision of a plurality of coils (two in this instance) renders it possible to vary the degree of heat by varying the connections of the coils; for example, for low heat both coils may be connected in series, while for yintermedia-te heat, only one coil may be active, and for high heat, both coils may be connected in parallel across the source.

To provide connections for these coils, a plurality of terminal bars 13 (Figs. 1' and l3) are provided, to which the ends of coils 11 and 12 may be connected, as by brazing or welding. These bars have free extremities extending away from the coils 11 and 12, and adapted to be received in appropriate plugs which may be stationarily supported on the oven structure. In this man -ner the lconnections to the element are rendered of, such anature `that the entire element may be removed from the oven and reinserted by simply exerting a small force suiicient to overcome the frictional force between the bars 13 and the cooperating contacts in the plug.

` The supporting struct-ure for the coils 11 and 12, as well as for the bars 13, includes a sheet metal base 14, which has a plurality of projections 15 stamped on its bottom side to serve as feet.- A number of double hooks 16 are appropriately supported on said base, the hooks 16 being forme-d preferably of refractory material, such as porcelain, and serving to hold the convolutions of the coils 11 and 12. These convolutions may assume any desired form, such as the parallel serl pentine arrangement indicated in Fig. 1. The important factors in carrying out the form of .'convolutions are to ensure that the two coils do not approach dangerously near each other, and that the lengths of both coils may be substantially evenly distributed l the coils as well as their configuration.

is most clearly disclosed in Figs. 4, 5 and 6. In the present instance there are two hook members 17 to each of the hooks 16, which are integrally supported on a common base. The hooks 17 point toward each other, and have cylindrical surfaces 18, two to each hook, and set so as to intersect at a corner 19. These cylindrical surfaces form the supports or seats for the coils 11 and 12, as well as the sides of the hook, and in order that these coils be given a substantial support, the hooks 16 are disposed in such manner on the base 14 that the cylindrical surfaces 18 are coaxial with the st-raight portions of the coils 11 and 12, as these coils pass obliquely between the hooks. The distance between the hooks 17 is large enough to permit the entry of t-hese coils between them.

Since the strai ht portions of coils 11 and 12 are paralleily to the edges of base 14, the double hooks 16 must be set at angles to these edges, as indicated in Fig. 1, in order to bring the cylindrical seats 18 into alinement with 'the coils. It is however, evident that the spacing of these hook members is mainly a matter of choice, and depends upon the number of supports that are needed fgr T e use of the hooks, ho-wever, permits a very rapid change of the coils 11 and 12, in case they be burnt ou't, without the necessity of laboriously threading these coils through narrow apertures, or of similarly arduous operations.

One of the important features of my invention resides in the simple and eiicient manner in which the hook members 16 are supported on the base 14. For this purpose each of these members is rovided with a pedestal or base 20 which 1s of larger size than the main body of the members 16. I prefer to make the sides of this base portion tapered as shown in Figs. 4 and 5, al-

though other forms cbuld also be used, so

long as it forms a shoulder upon which a clamping plate 21 may engage. This clamping plate has apertures corresponding with the positions of hook members 16. The sides of these apertures have slanting l1ps or projections 22 that engage with the sloplng shoulders of base 20, whereby the hook members are urged to-ward the base 14 and are held securely in position thereon. The clamping plate 21 is securely fastened by providing at two opposite sides thereof, a shoulder 23 (Fig. 2) over which the edge of base 14 may be turned. In addition, one or more bolts 36 (Fig. 1) may be used to assist in urging the plates 14 and 21 closely together, and thus in clamping the hooks 16 securely in place. The plate 21 may also be provided with sides 24 which may be turned over as at 25. In this manner an open boxlike structure is secured, within which the hooks 16 and elements 11 and 12 are disposed, as indicated in Fig. 3. The turned over edge permits the completed element to rest thereon, in case such a position is desired. The lower edge of the base 14 in the present instance is not shown as turned over on the clamping plate 21 ,I instead, as indicated in Fig. 3, it has an upturned portion 26 against which the side 24 of the clamping plate may rest. At the opposite side, the base 14 is left flat, the more easily to permit the conductor bars 13 to be supported.

These bars 13 are clamped between the insulation blocks 27 and 28, which are provided with appropriate slots for their accommodation. A dowel pin 29 carried by each bar ensures against longitudinal movement with respect to blocks 27 and 28. These blocks may be fastened together by the aid of the bars 30and 31 located in appropriate transverse grooves in the blocks, and of screws 32. These screws pass through the top bar 30 as well as theJ blocks 27 and 28, and are threaded into the bottom bar 31. The blocks 27 and 28 are supported from both the bottom and the sides of the clamping plate 21. This is accomplished by the aid of a sheet metal support 33, welded or brazed to the clamping har 95 31 and fastened as by rivetsl to the bottom of plate 21. This construction is clearly illustrated in Fig. 3. The support 33 has side flanges or vanes 34 which embrace the block 28. Parts of these anges are bent back at rightangles, as indicated at 35 (Fig. 1) whereby it may be also securely attached `to the side of the clamping plate 21. In order to facilitate the making of connections when necessary, a portion of the side of the plate 21 is cut away `opposite the blocks 27 and 28.

In case either or both of the coils 11 and 12 be burned out or need renewal for any reason, it is merely necessary to unfasten screws 32, remove block 27, take out from the block the appropriate bars connected i with the coil to be removed, and unhook that coil from the hook supports 16. A new coil with its bars 13 may now be inserted 115 in place of the old, and the clamping block 27 may be reattached to hold the conductor bars 13 in place. It is to be noted that the new coils replacing the old can be furnished complete with the bars 13 already welded 120 thereto, so that it is unnecessary to perform any welding at the scene of the replacement. This is a very important feature; in prior devices, terminal bars corresponding yto the bars 13 cannot be removed with ,125 the associated coil, and it is necessary to cut away the old coil and to Weld the new coil ends in place at the scene of the repair. The result may be, and often is, that the resistance coil thus installed has 130 not the right length which is required for proper heating. An unduly large or even dangerous current flow can exist, or else a lower degree of heat is produced than required. In other prior devices, clamping screws are used for the terminal bars, which in time rust or break oli', making repairs vor replacement extremely diiiicult. Furthermore, lthe fact that the coil must be threaded through narrow apertures makes it impossible to provide the terminal bars such as 13 ready welded before replacement. It is also likely that at some points the coil will be more stretched than at others. The result is uneven heating, and hot spots causing burn outs. Machine wound coils cannot therefore be used in such devices with any degree of success due to this fact; but with my invention, such machine wound coils may be manipulated readily without danger of unevenly stretching them. The re lacement can be very readily performed without danger of subsequent improper operation.

I claim:

1. In an electric heating element, a base, a plurality of hooks supported by the base, and a resistance element supported on said hooks, the spacing of the hooks being such that the element ma be placed thereon Without threading it t rough the hooks. 2. In an electric heating element, aV base, a plurality of hooks on said base, a resistance element supported on said hooks, and means for holding said hooks on sald .base, comprising a clamping plate having apertures permitting the hooks to project therethrough, the sides of the apertures engaging shouldersI on said hooks and urging them against the base.

3. In an electric heatingnelement, a metali 4lic base, a plurality of hooks of insulation material disposed on the base,.means for holding said hooks against displacement relatively to the base, and a resistance element supported on said hooks.

4. In an electric heating element, a metallic base, a plurality of hooks of insulation material disposed on the base, a resistance element supported on the hooks, and means my hand.

for holding said hooks against displacement relatively to the base, comprising an apertured clamping plate, the apertures in said plate permitting the hooks to project tlerethrough, said plate engaging a shoulder on each hook and.clamping 1t against the base.

5. An insulating support for a heating unit, comprising a. pair of hooks having their open sides opposite each other and separated by a substantial distance, and a base portion on which the hooks are supported, each of said hooks having a air of cylindrical seating surfaces arrange at an angle to each other and defining the sides of the hook, whereby an element may be seated on one side of one hook and on the opposite side of the other, when passing obliquely between the hooks.

6. In an electrical heating element, insulating supports, means for holding the supports in position,a heating unit held in said supports, and means forming connections for the unit, comprising a pair of slotted p insulation blocks,I bars fitting in the slots and fastened to the coil ends, and means for clamping the blocks together.

7. In an electrical heating element, a heating unit, means for insulatingly supportlng sald unit, connection bars connected to the ends of the unit, and means for detachably holdin said bars in place toform the terminalso the unit, comprising a pair of insulation blocks.

8.` In an electrical heating element, a heating unit, means for insulatmgly supporting saidunit, connection bars connected to the ends of the unit, an insulation block from which the bars may extend, means for Supporting said block, and means for detachably fastening the bars in said block.

9. In an electrical heating device, a pluing arranged one outside the other, the outer element having Va convolution that substantially evenly distributes the heat over the l"entire device.

In testimony whereof, I have hereunto set WILLIAM w. WEIR. f

vrality ofheating elements, and a support `for the elements, said heating elements be- 

